Sheet material forming apparatus



Aug. 16, 1966 A. FUST SHEET MATERIAL FORMING APPARATUS 3 Sheets-Sheet 1Filed April 5, 1963 INVENTOR. ARNOLD FUST ATTORNEY Aug. 16, 1966 A. FUSTSHEET MATERIAL FORMING APPARATUS 3 Sheets-Sheet 2 Filed April 5, 1965INVENTOR. ARNOLD FUST INVENTOR.

ARNOLD FUST Aug. 16, 1966 SHEET MATERIAL FORMING APPARATUS Filed April5, 1963 United States Patent 3,266,281 SHEET MATERIAL FORMING APPARATUSArnold Fust, Hnntingdon Valley, Pa., assignor to The Budd Company,Philadelphia, Pa., a corporation of Pennsylvania Filed Apr. 5, 1963,Ser. No. 270,921 5 Claims. (Cl. 72--177) This invention relates toapparatus for forming sheet material and, more particularly, toapparatus which, while not limited thereto, is especially useful forforming strips of full-hard, austenitic stainless steel.

Full hard, austenitic stainless steel, such as A.I.S.I. type 1, hasnumerous applications where high strength, hardness and abrasionresistance are important considerations. One such application is anabrasive strip for the leading edge of a helicopter rotor which issubject to abrasion by sand, rain, hail, etc. during operation of thehelicopter. However, difiiculties have been encountered in makingabrasive strips because the material is difficult to work and form.

One cause of these difficulties or problems arises because the strip isrnade from rolls of strip stock rolled to within the normal milltolerances of camber and buckle. lrior art apparatus has not been ableto satisfactory produce an abrasive strip from such roll stock becauseof its inability to both shape the part and to prevent the camber andexcess material, which produces the buckling, from ending up in andadversely affecting the final prodnot. The problem is furthercomplicated because the material cannot be elongated very much beforefracturing (8% for A.I.S.I. type 301 stainless steel) so that otherways, which are successful for more ductile material, cannot be used. Itis believed that the present invention is the only successful waypresently known for forming abrasive strips and similar elongated, sheetmetal objects of full-hard, austenitic stainless steel, such as A.I.S.I.type 301.

Accordingly, one of the objects of the invention is to provide improvedmeans for forming strips of high tensile sheet material.

Another object is to provide apparatus for forming strips of full hardstainless steel into elongated members of smooth or curved crosssection.

Still another object is to provide apparatus for forming abrasive stripsand similar objects of full hard, austenit-ic stainless steel.

A further object is to provide means for forming elongated, straightsheet metal parts of high strength materials 'wherein any excessmaterial in the stock strip is removed and does not enter into the finalproduct and cause buckling thereof.

Other objects and advantages will be apparent from the followingdescription taken in connection with the accompanying drawings wherein:

FIG. 1 is a side elevational view of a drawbench embodying theinvention;

FIGS. 2-9 are elevational views of dies shown in FIG. 1, FIGS. 2 and 7being in section and the others being end views with portions removed;

FIG. 10 is an enlarged and elevational view of one of the forming dies;

FIG. 11 is a vertical, longitudinal sectional view along reference lines1111 of FIG. 10;

FIG. 12 is an enlarged view of a detail enclosed in reference box 12 ofFIG. 11;

FIG. 13 is an enlarged end elevational of a portion of another one ofthe forming dies;

FIG. 14 is an enlarged cross sectional view along reference lines 1414of FIG. 1; and

3,266,281 Patented August 16, 1966 FIG. 15 is a schematic representationof a portion of the apparatus illustrated in FIG. 1 to indicate the pathof travel of the sheet material as the same is pulled through thesuccessive forming dies of the apparatus.

Referring now to the drawings, there is shown in FIG. 1 a conventionaldrawbench 15 comprising a bench 16 having a plurality of longitudinallyspaced housings .17 adjacent one end for supporting dies described morefully hereafter. The other end of the bench supports a dog 18 that isconnected to a power chain 19 driven so as to move the dog along thebench and pull a strip 20 of material from a supply roll 21 through thedies.

The dies, numbered 23-30, are divided into a series of bending dies 2327and a series of forming dies 28 30. As used in this description and inthe claims, the term bending means forcing the material into a differentshape without substantially exceeding the elastic limit and incurringany substantial permanent deformation, and the term forming meansforcing the material beyond its elastic limit and before its ultimatestrength to thereby permanently deform the material but without anyappreciable reduction in thickness.

The illustrated embodiment is designed to shape strip 20 so that it isstraight longitudinally and has an airfoil cross sectional shape similarto that shown in FIG. 14. This shaped comprises a pair of curved sides20a and 2% joined by a curved nose 20c substantially symmetrical aboutan axis extending from the center of the nose between the sides. Thiscross section is smoothly curved and has no sharp corners or tightbends.

With reference to FIG. 3, each of the bending dies cornprises a pair ofhard wood blocks 32 and 33 provided with a downwardly projecting malefinger 34 and an upwardly opening female recess 35 shaped similar to themale finger and spaced therefrom a distance equal to or slightly greaterthan the thickness of the strip.

The bending dies 23-27 are so constructed and arranged that as strip 20is pulled through them, the sides of the strip are progressively bentupwardly from a flat condition prior to die 23 into vertical positionsafter die 27 to provide a U-shape for smooth entry into the firstforming die. The bending dies thus preliminarily shape the strip priorto forming. If flat strip were to be fed directly to the first formingdie, the edges of the strip thus formed would be rippled.

Forming dies 28 and 29 are similar so that only one need be described indetail. With reference to FIGS. 10 and 11, die 28 comprises a leadingmale member or finger 38 and a trailing male member or finger 39disposed above a pair of leading and trailing female members 40 and 41mounted on the leading side of a housing 17 by a plurality of bolts 48.These bolts in conjunction with a pair of stop screws 49 permit verticaland lateral adjustment of the die parts and allow pressure to be appliedvia the fingers to the strip. The housings .17 upon which the formingdies are mounted are illustrated as being provided with Usha-ped slots42 for freely passing strip 20.

Fingers 38 and 39 and female members 40 and 41, along with thecorresponding parts of dies 29 and 30, are of a die material providinggood Wear properties without galling, pickup or die scoring. Onesuitable material is Ampco .grade 21 bronze, sold by Ampco Metals Inc.of Milwaukee, Wisconsin. This material is an aluminum bronze having thefollowing percentage weight composition:

Copper-Balance. Aluminum12.50-13.60. Iron3.505.00. Others-70.

3 When cast in a sand mold, this material has the following properties:

Tensile strength70,000 p.s.i. Yield strength5 0,000 p.s.i. Elongation(percent in 2 in. )-0.5. Brinell hardness (3,000 kg.)269.

The adjacent surfaces of each finger and the associated female memberare parallel, the surfaces being convex and concave, respectively, andcurved transversely but straight longitudinally. The surfaces areseparated a distance equal to the thickness of strip 20 whereby thestrip can be pulled through the dies. Screws 49 force the fingersagainst the strip but with a pressure below that which would producetearing or crocking of the strip. The surfaces are shaped to definetherebetween a gap having a transverse section similar in shape to thatof the finished product.

With reference to FIG. 12, as strip 20 is pulled through forming die 28,successive portions of the strip first pass between edges 43 and 44 andthen between edges 45 and 46. Because of the radial offset betweenfinger 38 and member 40 and finger 39 and member 41, edges 43 and 46 actas forming edges and edges 44 and 45 act as guiding edges. As the strippasses over each forming edge, its path of travel changes abruptly andthe opposite side of the strip is stretched beyond its elastic limit.Thus, each point on the strip travels along a longitudinal path whichhas abrupt angular transitions between the forming edges. Guiding edges44 and 45 hold strip 20 against the forming edges. In the absence ofguiding edges, the strip 20 would not incur any abrupt angulartransitions and it would tend to follow the dotted line path in FIG. 12wherein the opposite side would not be stretched sufficiently to incur apermanent set.

It has been found that the amount of deformation or set is dependent onthe angular transition, i.e., the degree of offset and the longitudinalgap between the adjacent fingers and female members. In FIG. 12,distance X is the longitudinal gap and distance y is the offset measuredin a longitudinal plane passing through the center of curvature of thedie parts. The gap can be varied by adding or taking away shims 50 andthe offset can be adjusted by loosening bolts 48 and screws 49. With aproper setting, determined by trial and error, the shape thus impartedto the strip will conform substantially to the shape of the spacebetween the trailing finger female member combination. With a givenoffset, an increase in the gap produces less forming and a decrease inthe gap produces more forming.

Die 28, as seen in FIGS. 12 and 15, is arranged to work the crosssection of the strip from nominal size as it passes over forming edge 43to under size as it passes over edge 46. The undersize differs from thenominal size by being smaller an amount equal to the offset. Thus, die28 works the strip from nominal to undersize.

Die 29 is similar to die 28 except that it is constructed to work thestrip from oversize to nominal. In this case, the oversize is greaterthan the nominal size by the amount of offset.

Die 30 is similar to dies 28 and 29 but differs because it is designedto work only the nose 20c of the strip. To accomplish this, die 30includes a pair of fingers 38' and 39 which are cut back at 51 along thesides of the strip to provide a finger clearance whereby only the noseportion is worked. Die 30 works the nose portion from oversize tonominal. This step has been found desirable since while, after pasingthrough dies 28 and 29, the sides are shaped within narrow tolerances,the nose might be out of tolerance and die 30 insures that the nose isshaped to within the tolerances.

The above described embodiment was designed to shape a 5 /2 wide stripof .009" thick, A.I.S.I. type 301, full hard, stainless steel and withthe material, the gap was .080" and the offset was .050" in each of dies28, 29 and 4 30. The mill tolerances for such a strip are A" camber per8 foot lengths and A" buckle per foot. With other thicknesses, materialsor shapes, the number of dies and the gaps and offsets will probablyvary.

With this setup, it was also found that any camber and buckle present inthe stock strip was removed and the end product was straight and freefrom buckles and ripples and had the same Width and thickness as theunshaped strip, as measured by conventional shop micrometers. That is,the shaping was accomplished without any noticeable reduction in size orarea. As the strip leaves ie 30, it has no transverse spring back.

The dog 18 clamps the end of the strip between a male finger 52 and afemale member 53 shaped to conform to the internal and external surfacesof the finished strip. Since the tension necessary to pull the stripthrough each forming die is well below the yield strength, the tensionat the dog can be made less than the yield strength so that the stripwill not tear or rupture due to the clamping action of the dog.

While the foregoing describes forming an airfoil cross section, it willbe obvious that the dies, by providing appropriate shapes can form othercross sectional shapes, such as airframe skins having only shallowcurvatures and can merely be used to remove excess material causingbuckling from stock strips, i.e., used to flatten and straighten strips.

While only a single embodiment has been illustrated, it will be apparentthat many changes can be made in the details and arrangement of partswithout departing from the scope of the invention as defined in theappended claims.

What is claimed is:

1. In apparatus for forming a substantially fiat strip of full hardaustenitic stainless steel into a strip of predetermined U-shapedcross-section, the combination comprising: drawbench means, means formounting a supply of sheet material at one end of said drawbench means,a plurality of bending die means mounted on and adjacent said one end ofsaid drawbench means, a plurality of forming die means mounted on anadjacent the other end of said drawbench means, means for advancing saidsheet material through said plurality of bending dies and said pluralityof forming dies, each of said bending die means having a male elementand a complimental female member spaced therefrom to admit a thicknessof sheet material therebetween for movement longitudinally of saiddrawbench means, said plurality of bending die means being effective toprogressively bend said sheet material from a flat condition to across-sectional form of U- shape without exceeding the elastic limit ofthe material, said plurality of forming die means each including leadingmale and female members with opposed surfaces separated a distance equalto the thickness of said sheet material and extending parallel to itsdirection of advancement to define a first passageway, and trailing maleand female members with like opposed parallel surfaces defining a secondpassageway, said first and second passageways being laterally offset onewith respect to the other relative to the direction of advancement ofsaid sheet material and being operative to stretch the same beyond itselastic limit, means associated with said forming die means to vary theoffset distance between said first and said second passageways, andadditional means associated with each of said plurality of forming diemeans to vary the longitudinal distance between said leading male andfemale members and said trailing male and female members.

2. In the apparatus as set forth in claim 1 wherein said plurality ofbending die means is effective to work the sheet material to a U-shapedform of nominal size, and wherein one of said plurality of forming diemeans has its leading male and female members disposed in an offsetrelation relative to its trailing male and female members and iseffective to work the sheet material so advanced from said nominal sizeto an undersize dimension.

3. In the apparatus as set forth in claim 2 wherein an additional one ofsaid plurality of forming die means disposed farther along in thedirection of advancement of said sheet material has its leading male andfemale memhers disposed in an offset relation relative to its trailingmale and female members and is effective to work the sheet material froman oversized condition of said U- shaped form to a nominal size thereof.

4. In the construction as set forth in claim 3 wherein a farther one ofsaid plurality of forming dies is effective to engage only the baseportion of the U-shaped form of said sheet material and coacts therewithto work the same from an oversize dimensional relationship to a nominalsize thereof.

5. In the apparatus set forth in claim 1 wherein said plurality offorming die means are of a Wear resistant, antigalling aluminum bronze.

References Cited by the Examiner UNITED STATES PATENTS 1,823,489 9/1931Ridder 72-176 2,395,651 2/1946 Anderson 72T76 2,960,140 11/1960 Anderson72--176 10 3,006,401 10/1961 Wognum et al 72-176 FOREIGN PATENTS 131,1534/1929 Switzerland.

15 CHARLES W. LANHAM, Primary Examiner.

W. H. JUST, Assistant Examiner.

1. IN APPARATUS FOR FORMING A SUBSTANTIALLY FLAT STRIP OF FULL HARDAUSTENITIC STAINLESS STEEL INTO A STRIP OF PREDETERMINED U-SHAPEDCROSS-SECTION, THE COMBINATION COMPRISING: DRAWBENCH MEANS, MEANS FORMOUNTING A SUPPLY OF SHEET MATERIAL AT ONE END OF SAID DRAWBENCH MEANS,A PLURALITY OF BENDING DIE MEANS MOUNTED ON AND ADJACENT SAID ONE END OFSAID DRAWBENCH MEANS, A PLURALITY OF FORMING DIE MEANS MOUNTED ON ANADJACENT THE OTHER END OF SAID DRAWBENCH MEANS, MEANS FOR ADVANCING SAIDSHEET MATERIAL THROUGH SAID PLURALITY OF BENDING DIES AND SAID PLURALITYOF FORMING DIES, EACH OF SAID BENDING DIE MEANS HAVING A MALE ELEMENTAND A COMPLIMENTAL FEMALE MEMBER SPACED THEREFROM TO ADMIT A THICKNESSOF SHEET MATERIAL THEREBETWEEN FOR MOVEMENT LONGITUDINALLY OF SAIDDRAWBENCH MEANS, SAID PLURALITY OF BENDING DIE MEANS BEING EFFECTIVE TOPROGRESSIVELY BEND SAID SHEET MATERIAL FROM A FLAT CONDITION TO ACROSS-SECTIONAL FORM OF USHAPE WITHOUT EXCEEDING THE ELASTIC LIMIT OFTHE MATERIAL, SAID PLURALITY OF FORMING DIE MEANS EACH INCLUDING LEADINGMALE AND FEMALE MEMBERS WITH OPPOSED SURFACES SEPARATED A DISTANCE EQUALTO THE THICKNESS OF SAID SHEET MATERIAL AND EXTENDING PARALLEL TO ITSDIRECTION OF ADVANCEMENT TO DEFINE A FIRST PASSAGEWAY, AND TRAILING MALEAND FEMALE MEMBERS WITH LIKE OPPOSED PARALLEL SURFACES DEFINING A SECONDPASSAGEWAY, SAID FIRST AND SECOND PASSAGEWAYS BEING LATERALLY OFFSET ONEWITH RESPECT TO THE OTHER RELATIVE TO THE DIRECTION OF ADVANCEMENT OFSAID SHEET MATERIAL AND BEING OPERATIVE TO STRETCH THE SAME BEYOND ITSELASTIC LIMIT, MEANS ASSOCIATED WITH SAID FORMING DIE MEANS TO VARY THEOFFSET DISTANCE BETWEEN SAID FIRST AND SAID SECOND PASSAGEWAYS, ANDADDITIONAL MEANS ASSOCIATED WITH EACH OF SAID PLURALITY OF FORMING DIEMEANS TO VARY THE LONGITUDINAL DISTANCE BETWEEN SAID LEADING MALE ANDFEMALE MEMBERS AND SAID TRAILING MALE AND FEMALE MEMBERS.